A. The Advantages of Xylitol
The most commonly used sweetener for food and pharmaceutical contexts is sucrose. Sucrose is used for its well-known sweetening properties and also for bulking purposes. Although a wide variety of alternate sweeteners are available, sucrose is generally considered to be the optimum sweetener with regard to taste profile and technological properties. However, sucrose has been implicated as a contributory factor in many diseases including hypertension, coronary heart disease, arterial sclerosis and dental caries. These health concerns have led health care professionals to analyze the effects of sucrose and its prominent role in the diet.
Perhaps the most significant, well-documented effect of sucrose is its contribution to tooth decay. The mouth contains a number of bacterial strains which ferment common dietary carbohydrates such as sucrose. This fermentation generates acid as an end product which lowers the pH in the mouth; the lowered pH leads to a demineralization of tooth enamel and finally to the formation of dental lesions or caries.
It is well known that it is not the total quantity of sugar consumed per se, but the frequency of consumption that contributes to dental caries. Thus, the presence of sucrose and other fermentable carbohydrates in regular meals is not the principal cause of tooth decay. The consumption of fermentable carbohydrates between meals in the form of confections and sweetened pharmaceuticals (and the frequency of such consumption) have been shown to have a close relationship to the formation of dental caries. Long after the candy or drug has been consumed, the fermentable carbohydrate stays in the mouth and is fermented by Streptococcus mutans and other cariogenic bacteria, lowering the mouth pH and promoting dental caries as described above.
One approach to fighting dental caries is to reduce or eliminate the amount of fermentable carbohydrates such as sucrose in pharmaceutical or food contexts. The replacement of fermentable carbohydrates by sugar substitutes which cannot be fermented, or are less easily fermented by S. mutans and other bacteria has been shown to decrease the development of dental caries.
Xylitol has been used as a sugar substitute in certain contexts (e.g. chewing gum: U.S. Pat. No. 4,514,422 (Yang) and 3,422,184 (Patel)) with practical and commercial success. The use of xylitol is attractive because of its taste and technological advantages. Xylitol is a naturally occurring five carbon sugar alcohol which has the same sweetness as sugar and a caloric content which is less than that of sugar. Xylitol is found in small amounts in many fruits and vegetables and is produced in the human body during normal metabolism. Xylitol is particularly attractive because of its known metabolic, dental and technical characteristics.
From a metabolic perspective, xylitol is metabolized largely independent of insulin, so it can be safely consumed by non-insulin dependent diabetics. Further, xylitol has been shown to delay gastric emptying and to possibly suppress food intake which means it may have an important role in weight reducing diets.
A significant advantage of xylitol is that it is not fermented by S. mutans and other bacteria found in the mouth and, therefore, does not produce acids which, as described herein, contribute to the formation of dental caries. Xylitol is well established as a non-cariogenic substance, i.e. xylitol does not contribute to caries formation. Significant data also exists which supports the view that xylitol is not only non-cariogenic, but actively suppresses the formation of new caries and may even reverse existing lesions by inducing remineralization, i.e. it is a cariostatic material. A summary of clinical data regarding the effects of xylitol and its possible mechanisms is set forth in Bar, Albert, Caries Prevention With Xylitol: A Review of the Scientific Evidence, 55 Wld. Rev. Nutr. Diet. 183-209 (1983). The mechanism or mechanisms by which xylitol effects any cariostatic properties is not yet known, but some possible mechanisms which have been suggested include a reduction of oral levels of S. mutans, a reduction in the development of plaque, the stimulation of the flow of protective saliva, the favorable alteration of the composition of saliva, the retardation of demineralization and an enhancement of remineralization of tooth enamel.
Xylitol also has significant technological advantages, particularly with respect to taste profile. Xylitol produces a pleasant cooling effect in the mouth when consumed in the crystalline state. The energy required to dissolve one gram of xylitol is 34.6 calories, the highest known value for sugars and sugar alcohols; this produces a physical cooling effect which is desirable in many contexts. Xylitol is as sweet as sugar and does not typically manifest unpleasant aftertastes.
Other polyols, such as sorbitol, mannitol, lactitol and others have also been substituted for sucrose in a variety of contexts. All of these polyols have certain advantages--such as non-cariogenicity--over sucrose. However, none of the other polyols have been demonstrated to have a cariostatic effect.
One context in which xylitol has been heretofore utilized with only limited success is as a constituent in tablets. In pharmaceutical contexts, tablets are used for bringing active substances into a size, shape and texture that can be dosaged, chewed, sucked, swallowed whole or dissolved in water for drinking. In food contexts, tablets can take the form of compressed, fruit or mint flavored confections which consist of a sweetener(s), flavor(s) and optionally color and acid. Because of its taste and cariostatic properties as described above, xylitol is a potentially attractive constituent in tablets for both food and pharmaceutical purposes Other polyols have been utilized in tablet contexts as diluents, flavoring agents and binders, but xylitol has not heretofore been used extensively in this context.
Sweetness in pharmaceutical tablets fulfills the purpose of making the product more pleasant to eat and to mask any unpleasant taste of the active ingredient(s). Today, many pharmaceutical tablets are sweetened with sucrose, lactose and other fermentable carbohydrates which are also used as diluents. Replacing sucrose and other fermentable carbohydrates with xylitol in those applications which must be sweetened would eliminate the use of cariogenic formulations in medicaments such as throat lozenges, cough tablets, vitamins, chewable tablets and others, and also takes advantage of the other attributes of xylitol discussed above, such as its noted cooling effect and metabolic characteristics.
In food contexts, tablets are usually sucked or chewed by the user and are often used as breath mints. Sucrose is the sweetener of choice in these contexts and has bulking properties as well. Replacing sucrose with xylitol would enable tablets to exploit the unique advantages of xylitol, particularly its anti-caries properties, and its pronounced cooling effect.
The cariostatic effect of xylitol is particularly important because clinical studies have shown that it is not the quantity of sucrose (or other acid producing substances such as maltose, lactose and dextrose), but the frequency of sucrose intake that is critical for caries development. Many pharmaceutical and food tablets are designed to be and are consumed at frequent and/or regular intervals throughout the day. For this reason, some dental researchers have suggested switching from sucrose, maltose, lactose, dextrose to a non-acid producing sweetener such as xylitol in pharmaceutical and food contexts.